two additional points. Mounted shooting on a moving horse requires balance/center of gravity, just like when you are shooting from the ground. If you are a woman or teaching women to shoot, or are a woman teaching men how to shoot keep in mind a very fundamental point. Women and men have a different center of gravity/balance. They need different stances to be "balanced to their selves" My sense of balance/ stance will be different than yours. Let them understand the importance of balance and then let them find out what works in a dry fire practice. The same goes for grip. My wife could not get the grip I thought she should have. I said OK here is the "unloaded gun" find out what works. She ignored her thumb and found it more important to wrap her fingers around the front of the grip and over lap the ones from the other hand. Her thumb then found a niche that works for her. Shooting 40 cal she now has a stance and grip that she flows into as the gun comes to play. She is much more likely to end up in THAT stance if she ever has to, than one I would try to shoehorn her into.
Just my uneducated opinions, delete as necessary
PS I am a good balloon killer, but I just can't seem to get my horse to find a stance he likes.